The treatment of body lumens that have an undesired reduced diameter is often difficult because of an inability to determine the natural diameter of the lumen. For example, the healthy and normal diameter of a blood vessel may be unknown when the blood vessel has an undesired reduced diameter. For example, in a patient suffering from an acute myocardial infarction, the proper selection of a stent for treatment of the blood vessel is difficult because the diameter of the blood vessel has suddenly changed. Various factors can cause such changes, such as contractile spasms of the blood vessel and/or the presence of blood clots (thrombi).
Treating bodily conduits that have an undesired reduced diameter by means of a radially expandable tubular implant with a cutout or meshed structure, currently called a “stent,” is known. This device may be introduced in an unexpanded/contracted state into the conduit to be treated and delivered to the area of the conduit that has an undesired reduced diameter. The device is then radially expanded, particularly by means of an inflatable balloon, or, when it has a self-expandable structure, the stent may be released from a sheath that contains the stent in its contracted state.
As discussed above, various stents are available to treat such conditions, including balloon-expandable stents and self-expanding stents. When using stents, those of ordinary skill in the art sometimes select an expanded stent size of 100-120% of the presumed normal size of the lumen. That is, the stent is allowed to expand within the target location to a size that is the same size as the presumed normal size of the target location, up to a size that is 20% larger than the presumed normal size of the target location. This can ensure that the stent is not under-sized, and thus that the stent is firmly anchored in place. With self-expanding stents in particular, it further ensures that there is continuous radial force anchoring the stent in place.
When balloon-expandable stents are selected in place of self-expanding stents, great care (and thus extra time in a situation such as a myocardial infarction where time is of the essence in treatment) must be taken in selecting an appropriately sized stent to avoid any danger that the stent may be under-sized when fully expanded. However, issues may remain due to the possibility of the lumen size continuing to change over time, and over-sizing of balloon-expanded stents might cause damage such as rupture of a lumen wall. In addition, with any stent that remains in the lumen, the stent itself may cause problems over time, such as causing thrombosis formation within a blood vessel. This is even more relevant with drug eluting stents, e.g., stents that elute anti-restenotic drugs, since the polymer coating on these stents may be responsible for late stent thrombosis when the stent is not well apposed to the vessel wall. Such issues could be addressed by bioresorbable stents.
There remains a demand for methods for effectively treating bodily conduits, for example, bodily conduits that have an undesired reduced diameter.